Toluene sulfonic acid compositions



United States Patent 3,458,449 TOLUENE SULFDNIC ACID COMPOSITIONS Marvin Mausner, Teaneck, Richard D. Kats'tra, Hackcnsack, and Gerald Spiegelman, Hohoken, N.J., assignors to Witco Chemical Company, Inc., New York, N.Y.,

a corporation of Delaware No Drawing. Filed Dec. 19, 1966, Ser. No. 602,542

Int. Cl. B011: 11/06 U.S. Cl. 252182 Claims ABSTRACT OF THE DISCLOSURE Production of an improved toluene sulfonic acid composition which consists essentially of a normally liquid mixture of (a) from about 25 to about 90% toluene sulfonic acid, and (b) from about 75 to about 10% of benzene sulfonic acid and/or a monoand/or di-alkyl benzene sulfonic acid in which the total of the carbon atoms in the alkyls is from 2 to 9, said percentages being by weight.

This invention relates to novel and highly useful mixtures of certain aromatic sulfonic acids containing toluene sulfonic acid and more particularly to substantially anhydrous sulfonic acid mixtures containing a substantial portion of toluene sulfonic acid in admixture with certain alkyl benzene sulfonic acids, especially xylene sulfonic acids, which are liquid at ambient and at materially lower temperatures, and to a process of making the same.

Benzene sulfonic acid and lower alkyl benzene sulfonic acids, particularly where the alkyl radical contains 1 to 4 carbon atoms, and the salts thereof are well known and used commercially as catalysts in polymerization, alkylation and esterification reactions and as solubilizers, coupling agents, or anticaking agents in detergents. Typical of such materials are benzene sulfonic acid, as mentioned, toluene sulfonic acid, cumene sulfonic acid, xylene sulfonic acid and the sodium and potassium salts of said acids.

Toluene sulfonic acid, particularly, has been utilized extensively as a polymerization, alkylation, and esterification reaction catalyst. Because of its high melting point, the substantially anhydrous free toluene sulfonic acid being a semisolid at 25 degrees C. and higher, storage and handling problems are encountered. More specifically, if anhydrous toluene sulfonic acid is stored at ambient temperature of about 25 degrees C., it is necessary to heat the material to at least about 50 degrees C. to keep it fluid.

In accordance with our present invention, hereafter described in detail, we have discovered that admixtures of toluene sulfonic acid with benzene sulfonic acid or monoor di-alkyl benzene sulfonic acids, in which the alkyl radicals may be straight or branched chain and have a total of from 2 to 9 carbon atoms, in certain proportions with respect to each other, as stated below, in the form of substantially anhydrous liquids, having a maximum Water content of about 1.5% and preferably less than 1%, remain liquid at temperatures of about degrees C. or lower. Not only are storage and handling of said admixture facilitated but, as we have discovered, lower reaction temperatures are possible when said admixture is utilized as a catalyst. Further, increasing reaction rates in certain systems are also possible.

The amounts or proportions of the toluene sulfonic acid utilized in the admixtures thereof with benzene-sulfonic acid or the aforesaid alkyl benzene sulfonic acids are variable, being dependent, for instance, upon the desired melting point of the resulting mixture. In general, the percentage will range from about 25 to 90%, by weight, of toluene sulfonic acid and 75 to 10%, by weight, of benzene sulfonic acid or the aforesaid alkyl benzene sulfonic acids. Especially suitable are sulfonic acid mixtures containing from about 50 to toluene sulfonic acid and from about 50 to 25% of benzene sulfonic acid or the aforesaid alkyl benzene sulfonic acids.

While mixtures of alkali metal toluene sulfonates and alkali metal xylene sulfonates have been utilized as solubilizers in detergent compositions, as disclosed, for instance, in U.S. Patent No. 2,859,182, the existence of compositions in the form of mixtures of the free sulfonic acids and their surprising properties have heretofore not been known nor suggested. Our invention, as indicated above, is based uopn these discoveries as well as upon particularly advantageous processes for preparing mixtures of the free acid form of toluene sulfonic acid with benzene sulfonic acid or the aforesaid alkyl benzene sulfonic acids, as herein disclosed.

Various procedures for preparing, individually, toluene sulfonic acid, benzene sulfonic acid and lower alkyl benzene sulfonic acids, are known to the art. The production of sulfonated alkyl benzenes, by reacting an excess of the alkyl benzene with sulfuric acid, for instance, involves vacuum distillation techniques at elevated temperatures to strip the sulfonic acid of water and excess solvent. Lower distillation temperatures are beneficial in achieving a product with more desirable color properties and a minim-um of reaction by-products such as sulfones.

While the compositions of our invention can be made by independently sulfonating toluene, and independently sulfonating benzene or an alkyl benzene such as xylene, and then admixing the toluene sulfonic acid and the xylene sulfonic acid in the requisite proportions, we have found it especially advantageous to produce the compositions of our invention by the following procedure which, in general, involves initial sulfonation of the higher boiling of the toluene and the benzene or monoor di-alkyl benzene with excess 100% sulfuric acid or oleum until less than about 0.5% of the organic solvent remains, this reaction being generally carried out at about 70 degrees C.; then adding the lower boiling solvent in about 25% excess, the reaction being carried out under reflux conditions, water being removed azeotropically during reflux; (in some cases, the lower boiling solvent may initially be sulfonated if there is an azeotropic advantage to be gained in the second step or if reaction time may be reduced); then, upon attainment of less than about 0.7% residual sulfuric acid, the remaining water is removed azeotropically under vacuum reflux at about degrees C. until the water level is at about 1.0%; then removing the bulk of the remaining solvent by vacuum distillation preferably at about degrees C.; and finally removing residual solvent by vacuum stripping, preferably :at 140 degrees C. maximum and maximum vacuum, exposure to high temperature being kept to a minimum to avoid excessive sulfone formation.

Thus, for instance, in accordance with the most advantageous procedure for producing the compositions of the present invention, benzene, or lower alkyl benzene in which the total carbon atoms in the alkyl or 'alkyls is from 2 to 9, for instance, xylene, cumene, or octyl benzene, and especially xylene or cumene, is sulfonated with a stoichiometric excess of concentrated sulfuric acid, or oleum, desirably %104% H 80 for about at least 2 hours, until only minor amounts of free benzene or alkyl benzene remain. An excess amount of toluene, preferably about 25 excess, is then added and sulfonation is continued under azeotropic reflux conditions, usually for at least about 20 to 30 hours in plant scale operations, until essentially no unreacted sulfuric acid remains, and a substantial portion of the water of reaction has been removed. The remaining water of reaction and excess solvent are then stripped to a low level by vacuum distillation. By first sulfonating the higher boiling solvent, stripping off excess solvent can be achieved at lower temperatures since the excess solvent will consist principally of toluene.

The sulfonation reaction between the benzene or the alkyl benzene and excess sulfuric acid is generally carried at a temperature between about 60 degrees C. and 80 degrees C. and preferably betweeen about 65 degrees C. and 70 degrees C. The sulfonation reaction betweeen the unreacted sulfuric acid and excess toluene is best carried out at the reflux temperature of the mixture, preferably between about 110 degrees C. and 120 degrees C. and the temperature should not exceed about 140 degrees C.

Stripping of excess water of reaction and solvent is' generally accomplished by first drawing a partial vacuum on the reaction vessel, between about 15 to 20 inches of mercury vac. and refluxing the reaction mixture to permit azeotropic distillation to occur at a temperature of between about 80 degrees C. and 90 degrees C. When a satisfactorily low water level has been attained, a full vacuum is drawn on the reaction vessel, usually at least about 28.5 inches of mercury vac., and the bulk of excess unreacted solvent is distilled off at a temperature between about 80 degrees C. and 90 degrees C. Residual solvent is then removed by vacuum stripping at a maximum temperature of about 140 degrees C. advantageously under a full vacuum of at least about 28.5 inches of mercury vac., for a brief period of time, not to exceed about one hour and preferably not longer than about 30 minutes.

The following examples are illustrative of the practice of the present invention but they are not to be construed in any way as limitative of the full scope of the invention since various changes and modifications can be made in the light of the guiding principles and teachings disclosed herein.

EXAMPLE 1 Into a 2000 gallon glass-lined jacketed vessel, provided with a reflux device, 444 gallons of xylene were added at room temperature while agitating. Then, 400 gallons of 100% H 80 were added over a period of time so that the reactor temperature did not exceed 65 degrees C. The resulting mixture was then warmed to between about 65 degrees C. and 70 degrees C. and maintained at this temperature for about 5 hours. Then, 1036 gallons of toluene were added to the reactor and the mixture was heated by steam in the jacket to about 120 degrees C. and azeotropically refluxed for about 35 hours while miantaining the temperature at about 120 degrees C. after which time substantially all the sulfuric acid had been reacted. The reaction batch was allowed to cool to between about 80 degrees C. and 90 degrees C. and maintained at that temperature by using steam in the jacket. A partial vacuum of about to inches of mercury was then drawn on the reaction vessel and the batch was allowed to reflux azeotropically until substantially all the remaining water of reaction had been removed. When a satisfactory moisture level was reached, a full vacuum of at least about 28.5 inches of mercury was drawn on the reaction vessel and, while maintaining a temperature of between about 80 degrees C. and 90 degrees C., the batch was allowed to distill to remove unreacted toluene which was collected. Final solvent stripping was accomplished by maintaining the reaction vessel under a full vacuum of at last 28.5 inches of mercury and heating the reaction batch to a temperature between about 125 degrees C. and 130 degrees C. When it was determined that the unreacted solvent level had reached a satisfactory level, the batch was cooled to below 50 degrees C. and transferred to storage drums.

The resulting batch was found to have a melting point of 10 degrees C., a minimum sulfonic acid active level of 95%, a maximum of 1.5% water, 2.0% max. H 80 negligible amounts of unreacted solvent and nominal amount of sulfone impurities.

EXAMPLE 2 Into a 4-liter reaction flask equipped with stirrer, thermometer and reflux condenser were placed 300 g. of cumene while agitating. Then, 530 g. of H 80 were added slowly so that the reactor temperature did not exceed 65 degrees C. The resulting mixture was then warmed to about 70 degrees C. and maintained at this temperature until less than 0.5% cumene remained, which took about 2 hours. Then, 550 g. of toluene, about a 25% stoichiometric excess, were added to the reactor and the mixture was heated to between about degrees C. and degrees C., at which time refluxing of the mixture was initiated and water was azeotropically removed. Refluxing was continued for about 18 hours at which time it was determined that less than 0.7% residual H 50 remained. The reaction batch was allowed to cool to about 80 degrees C. and maintained at that temperature while a partial vacuum of about 15 inches of mercury vac. was drawn and maintained on the reaction vessel. The reaction vessel was refluxed while the remaining water was azeotropically removed. A satisfactory final water level was attained after about 1 hour. A full vacuum of at least 28.5 inches of mercury vac. was then drawn on the reaction vessel and the temperature of the batch was raised to about 90 degrees C. The bulk of the excess solvent was then distilled off. Residual solvent was stripped off by then heating the batch under full vacuum at about degrees C. to degrees C. for 30 minutes. The reaction batch was then cooled to room temperature. The resulting mixture was a clear liquid at room temperature. The active sulfonic acid level of the batch was determined to be 96.5% and negligible amounts of unreacted solvent and water were found. The melting point of the batch was 8 degrees C.

EXAMPLE 3 570 g. of xylene, 1645 g. of 100% H CO and 1905 g. of toluene were used in this example to prepare a substantially anhydrous, liquid sulfonic acid mixture containing about equal percentages by weight of xylene sulfonic acid and toluene sulfonic acid, utilizing the procedure of Example 2. The melting point of the final product was 1O degrees C.

EXAMPLE 4 570 g. of xylene, 1645 g. of 100% H SO and 1095 g. of toluene were used in this example to prepare a substantially anhydrous, liquid sulfonic acid mixture containing about 33% xylene sulfonic acid and about 67% toluene sulfonic acid by weight, utilizing the procedure of Example 2. The melting point of the final product was about 15 degrees C.

EXAMPLE 5 247 g. of benzene, 595 g. of 100% H 80 and 555 g. of toluene were used in this example to prepare a substantially anhydrous, liquid mixture of about equal parts by weight of toluene sulfonic acid and benzene sulfonic acid, utilizing the procedure of Example 2. The melting point of the final product was 5 degrees C. In carrying out this example, it is preferable to start the sulfonation reaction with the benzene and then add the toluene, and finally to strip off excess unreacted toluene. It may also be noted that, whereas the melting point of the final product of this example was 5 degrees C., toluene sulfonic acid and benzene sulfonic acid, individually, are not liquid at this low temperature.

EXAMPLE 6 354 g. of octyl benzene, 470 g. of 100% H SO and 550 g. of toluene were used in this example to prepare a substantially anhydrous, liquid mixture of substantially equal parts by weight of octyl benzene sulfonic acid and toluene sulfonic acid, utilizing the procedure of Example 2. The melting point of the final product was 5 degrees C.

The compositions of the present invention, as prepared as indicated above, consist essentially of normally liquid mixtures of (a) toluene sulfonic acid and (b) benzene sulfonic acid and/ or monoor di-alkyl benzene sulfonic acids in which the total of the carbon atoms in the alkyls is from 2 to 9, the active sulfonic acid constituents being well over 90%, by weight. As indicated above, small percentages of unreacted toluene and/or benzene or monoand/or di-alkyl benzenes, sulfuric acid, and sulfones, etc. formed in the reaction will usually be present but they have no particularly adverse effect on the utilities of the compositions for their usual purposes. Thus, a typical composition comprising a mixture of approximately equal parts, by weight, of toluene sulfonic acid and xylene sulfonic acid, made in accordance with our invention, may contain not less than about 95 or 96% of said mixture of sulfonic acids, not more than about 0.4% of toluene and/ or xylene, not more than about 1.5% sulfones, not more than about 1.5% water, not more than about 2% free sulfuric acid, and not more than about 1% water insolubles.

What we claim as new and desire to protect by Letters Patent of the United States is:

1. A process for producing a substantially anhydrous liquid mixture consisting essentially of (a) from about 25% to about 90% by weight of toluene sulfonic acid and (b) from about to 75% by weight of at least one member selected from the group consisting of benzene sulfonic acid and monoand di-alkyl benzene sulfonic acid in which the alkyl radicals have a total of from 2 to 9 carbon atoms, which comprises initially reacting the aforesaid (b) ingredient with a stoichiometric excess of sulfuric acid at a temperature between about 60 and 80 degrees C. until said (b) ingredient is substantially completely sulfonated, then adding a stoichiometric excess of toluene, heating the reaction mixture to reflux temperatures and azeotropically refluxing the reaction mixture until substantially all of the sulfuric acid is converted into the sulfonic acid, cooling the reaction mixture while maintaining an azeotroping temperature, and azeotropically refluxing under a partial vacuum until substantially all of the remaining water has been removed,

and then distilling ofi, under vacuum, substantially all of the unreacted toluene from the reaction batch.

2. A process according to claim 1, in which the sulfo- -nating agent is 100 to 104% sulfuric acid.

3. A process according to claim 1, in which the re- 7 action mixture, after the sulfonating reactions, is cooled vto between about degrees C. and degrees C., and

the azeotroping and distilling steps are carried out at temperatures between about 80 degrees C. and 90 degrees C.

4. A process according to claim 3, in which the distilling otf of the unreacted toluene is effected under a vac- -uum of at least about 28.5 inches of mercury.

5. A process according to claim 4, in which the (b) ingredient is xylene.

6. A process according to claim 4, in which the (b) ingredient is cumene.

7. A composition consisting essentially of a normally liquid mixture of (a) from about 25 to about 90% toluene sulfonic acid, and (b) from about 75 to about 10% of at least one member selected from the group consisting .of benzene sulfonic acid and monoand di-alkyl benzene References Cited UNITED STATES PATENTS 2,389,041 11/1945 Gould 260505 2,848,483 8/1958 Reif et a1. 260-505 2,889,360 6/1959 Brooks 2-60505 LEON D. ROSDOL, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R. 

